Light emitting device

ABSTRACT

Disclosed is a light emitting device including a substrate, a light emitting structure arranged on the substrate, the light emitting structure including a first semiconductor layer, a second semiconductor layer and an active layer arranged between the first semiconductor layer and the second semiconductor layer, a first electrode electrically connected to the first semiconductor layer, and a second electrode electrically connected to the second semiconductor layer, wherein the light emitting structure has a top surface including a first side and a second side which face each other, and a third side and a fourth side which face each other.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the priority benefit of Korean PatentApplication No. 10-2010-0126126, filed on in Korea Dec. 10, 2010, thedisclosure of which is incorporated herein by reference.

BACKGROUND OF THE EMBODIMENT

1. Field

This relates to a light emitting device.

2. Background

Fluorescent lamps go against the trend towards environmentalfriendliness-oriented next generation lighting systems due to frequentreplacement caused by black spots, short lifespan or the like and use ofphosphor materials and alternative light sources are thus gradually usedinstead of fluorescent lamps.

Light emitting diodes (LEDs) attract the most attention as such otherlight source. LEDs are interesting as next generation light sourcesowing to semiconductor advantages including rapid processing speed andlow power consumption, as well as environmental friendliness andexcellent energy saving effects. Accordingly, application of LEDs asalternatives to conventional fluorescent lamps is actively conducted.

Recently, semiconductor light emitting devices such as LEDs are appliedto a variety of displays including televisions, monitors, notebookcomputers, cellular phones and displays and, in particular, are widelyused as backlight units instead of conventional CCFLs.

At present, there is a need for high brightness in order to use lightemitting devices as light sources. In an attempt to realize highbrightness, research associated with manufacture of light emittingdevices to uniformly diffuse current and thereby increase luminousefficacy is underway.

BRIEF DESCRIPTION OF THE DRAWINGS

The embodiments will be described in detail with reference to thefollowing drawings in which like reference numerals refer to likeelements wherein:

FIG. 1 is a plan view illustrating a light emitting device in accordancewith an embodiment as broadly described herein;

FIG. 2 is a cross-sectional view taken the line A-A of the lightemitting device shown in FIG. 1;

FIG. 3 shows test data of luminous efficacy of the light emitting deviceshown in FIG. 1;

FIG. 4 is a plan view illustrating a light emitting device in accordancewith another embodiment as broadly described herein;

FIG. 5 is a plan view illustrating a light emitting device in accordancewith other embodiment as broadly described herein;

FIG. 6 is a perspective view of a light emitting device packageincluding the light emitting device in accordance embodiments as broadlydescribed herein;

FIG. 7 is a perspective view of a backlight unit including a lightemitting device in accordance embodiments as broadly described herein;

FIG. 8 is a sectional view of the lighting device taken along the lineA-A of the lighting device shown in FIG. 7;

FIG. 9 is a perspective view of a liquid crystal display including alight emitting device in accordance with an embodiment as broadlydescribed herein;

FIG. 10 is a perspective view of a liquid crystal display including alight emitting device in accordance with another embodiment as broadlydescribed herein;

DETAILED DESCRIPTION

Reference will now be made in detail to the preferred embodiments,examples of which are illustrated in the accompanying drawings.

Advantages and characteristics and methods for addressing the same willbe clearly understood from the following embodiments taken inconjunction with the annexed drawings. However, embodiments are notlimited and may be realized in other various forms. The embodiments areonly provided to more completely illustrate and to render a personhaving ordinary skill in the art to fully understand the scope. Thescope is defined only by the claims. Accordingly, in some embodiments,well-known processes, well-known device structures and well-knowntechniques are not illustrated in detail to avoid unclearinterpretation. The same reference numbers will be used throughout thespecification to refer to the same or like parts.

Spatially relative terms, “below”, “beneath”, “lower”, “above”, “upper”and the like may be used to indicate the relationship between one deviceor constituent elements and other devices or constituent elements, asshown in the drawings. It should be understood that the spatiallyrelative terms include the direction illustrated in the drawings as wellas other directions of devices during use or operation. For example, ina case in which the device shown in the drawing is reversed, a devicearranged “below” or “beneath” the other device may be arranged “above”the other device. Accordingly, the exemplary term, “beneath” may include“below” or “beneath” and “above”. The device may be arranged in otherdirections. As a result, the spatially relative terms may be construeddepending on orientation.

Terms used in the specification are only provided to illustrate theembodiments and should not be construed as limiting the scope and spiritof the present invention. In the specification, a singular form of termsincludes plural forms thereof, unless specifically mentioned otherwise.In the term “comprises” and/or “comprising” as used herein, thementioned component, step, operation and/or device is not excluded frompresence or addition of one or more other components, steps, operationsand/or devices.

Unless defined otherwise, all terms (including technical and scientificterms) used herein may be intended to have meanings understood by thoseskilled in the art. In addition, terms defined in general dictionariesshould not be interpreted abnormally or exaggeratedly, unless clearlyspecifically defined.

In the drawings, the thicknesses or sizes of respective layers areexaggerated, omitted or schematically illustrated for clarity andconvenience of description. Therefore, the sizes of respective elementsdo not wholly reflect actual sizes thereof.

In addition, angles and directions referred to during description of astructure of a light emitting device are described based on illustrationin the drawings. In the description of the structure of the lightemitting device, if reference points with respect to the angles andpositional relations are not clearly stated, the related drawing will bereferred to.

Hereinafter, for further detailed illustration of the shape of the lightemitting device according to embodiments, the light emitting device willbe described based on a first direction (X) and a second direction (Y)vertical to the first direction (X).

FIG. 1 is a plan view illustrating a light emitting device in accordancewith an embodiment as broadly described herein, FIG. 2 is across-sectional view taken the line A-A of the light emitting deviceshown in FIG. 1, and FIG. 3 shows test data of luminous efficacy of thelight emitting device shown in FIG. 1.

With reference to FIGS. 1 and 2, a light emitting device 110 as embodiedand broadly described herein may include a substrate 110, a lightemitting structure 145 including a first semiconductor layer 120, asecond semiconductor layer 140 and an active layer 130 arranged betweenthe first semiconductor layer 120 and the second semiconductor layer140, a first electrode 160 arranged on the first semiconductor layer 120and a second electrode 170 arranged on the second semiconductor layer140.

The substrate 110 is a substrate which is suitable for growingsemiconductor single crystals and is, for example, made of alight-transmitting material containing sapphire (Al₂O₃), and thematerial may be at least one of Si, GaAs, Si, GaP, InP, Ge, Ga₂0₃, ZnO,GaN, SiC and AlN, without being limited thereto.

Impurities present on the surface of the substrate 110 may be removed bywet-washing and the substrate 110 may be a patterned substrate (PSS),the surface of which is patterned with a light extraction pattern toimprove light extraction efficiency, but is not limited thereto.

In addition, the substrate 110 may be a material which facilitatesemission of heat and thereby improves thermal stability.

Meanwhile, an anti-reflective layer (not shown) may be arranged on thesubstrate 110 and the anti-reflective layer is commonly called an “ARcoating layer”, which basically utilizes interference between lightreflected from a plurality of interfaces. That is, the AR coating layerrenders the status of light reflected from different interfaces to betilted at an angle of 180 degrees, offsets the light, and reducesstrength of the reflected light, although it is not limited thereto.

In addition, a buffer layer 111 may be arranged on the substrate 110 toreduce lattice mismatch between the substrate 110 and the light emittingstructure 145 and facilitate growth of a plurality of semiconductorlayers.

The buffer layer 111 may be grown in the form of a single crystal on thesubstrate 110 and the buffer layer 111 grown as the single crystal mayimprove crystallinity of the light emitting structure 145 grown on thebuffer layer 111.

In addition, the buffer layer 111 may be formed at a low temperature andfor example may contain at least one of GaN, InN, AlN, AlInN, InGaN,AlGaN, and InAlGaN, although the material for the buffer layer 111 isnot limited thereto.

That is, the buffer layer 111 may have an AlInN/GaN laminate structure,an InGaN/GaN laminate structure, or an AlInGaN/InGaN/GaN laminatestructure or the like.

The first semiconductor layer 120 may be arranged on the substrate 110or the buffer layer 111. When the first semiconductor layer 120 isrealized as an n-type semiconductor layer, the first semiconductor layer120 may be selected from semiconductor materials having a formula ofIn_(x)Al_(y)Ga_(1-x-y)N (0≦x≦1, 0≦y≦1, 0≦x+y≦1), such as GaN, AlN,AlGaN, InGaN, InN, InAlGaN, AlInN and may be doped with an n-type dopantsuch as Si, Ge, Sn, Se and Te.

At this time, an undoped semiconductor layer (not shown) which is notdoped with a dopant may be arranged between the first semiconductorlayer 120 and the buffer layer 111, the undoped semiconductor layer isformed to improve crystallinity of the first semiconductor layer 120 andmay be the same as the first semiconductor layer 120 except that theundoped semiconductor layer exhibits lower electrical conductivity thanthe first semiconductor layer 120 since it is not doped with an n-typedopant, although it is not limited thereto.

An active layer 130 may be arranged on the first semiconductor layer 120and the active layer 130 may have a mono- or multi-quantum wellstructure, a quantum-wire structure, or a quantum dot structure or thelike, composed of a compound semiconductor material of Group III-Velements.

In the case where the active layer 152 has a quantum well structure, forexample, it may have a mono- or multi-quantum well structure including awell layer having the formula of In_(x)Al_(y)Ga_(1-x-y)N (0≦x≦1,0≦y≦x≦1, 0≦x+y≦1) and a barrier layer having the formula ofIn_(a)Al_(b)Ga_(1-a-b)N (0≦a≦1, 0≦b≦1, 0≦a+b≦1). The well layer may bemade of a material having a band gap smaller than that of the barrierlayer.

In addition, a conductive clad layer (not shown) may be arranged onor/and under the active layer 130 and the conductive clad layer may bemade of an AlGaN-based semiconductor and may have a band gap larger thanthat of the active layer 130.

A second semiconductor layer 140 may be arranged on the active layer 130and may be realized with a p-type semiconductor layer. In a case inwhich the second semiconductor layer 140 is realized with a p-typesemiconductor layer, the second conductive semiconductor layer 140 mayfor example be made of a semiconductor material having a formula ofInxAlyGa1-x-yN (0≦x≦1, 0≦y≦1, 0≦x+y≦1) such as GaN, AlN, AlGaN, InGaN,InN, InAlGaN and AlInN and may be doped with a p-type dopant such as Mg,Zn, Ca, Sr and Ba.

The first semiconductor layer 120, the active layer 130 and the secondsemiconductor layer 140 may be formed by a method which includes, but isnot limited to, metal organic chemical vapor deposition (MOCVD),chemical vapor deposition (CVD), plasma-enhanced chemical vapordeposition (PECVD), molecular beam epitaxy (MBE), hydride vapor phaseepitaxy (HVPE) or the like.

In addition, the concentrations of n-type and p-type dopants doped inthe first semiconductor layer 120 and the second semiconductor layer 140may be uniform or non-uniform. That is, the structure of a plurality ofsemiconductor layers may be varied and is not limited.

In addition, unlike those mentioned above, the first semiconductor layer120 may include a p-type semiconductor layer and the secondsemiconductor layer 140 may include an n-type semiconductor layer.Accordingly, the light emitting structure 145 may have at least one ofn-p, p-n, n-p-n and p-n-p junction structures.

That is, the light emitting structure 145 may have a structure in whichthe position of the first and second semiconductor layers 120 and 140arranged based on the active layer 130 is switched, but in the followingdescription, the first semiconductor layer 120 includes an n-typesemiconductor layer and is arranged on the substrate 110.

Here, the light emitting structure 145 may have a top surface includingfirst and second sides S1 and S2 which face each other, and third andfourth sides S3 and S4 which face each other and cross the first andsecond sides S1 and S2, respectively.

That is, when seen from the top of the light emitting structure 145, thefirst and second sides S1 and S2 may face each other, and the third andfourth sides S3 and S4 may face each other.

In addition, although the first side S1 is arranged in an upper part andthe second side S2 is arranged in a lower part in the drawing, thearrangement is not limited thereto. That is, the first side S1 may bearranged in a lower part and the second side S2 may be arranged in anupper part.

In addition, although the third side S3 is arranged in a left part andthe fourth side S4 is arranged in a right part in the drawing, thearrangement is not limited thereto. That is, the position of the thirdside S3 and the fourth side S4 may be switched.

The first to fourth sides S1 to S4 is set based on the position seenfrom the top of the light emitting structure 145.

The first electrode 160 may be electrically connected to the firstsemiconductor layer 120. The first electrode 160 may be formed on thefirst semiconductor layer 120 and may include a first electrode pad 162and a first electrode arm 164.

In addition, the first electrode 160 may be formed in the exposed partof the first semiconductor layer 120. That is, in the light emittingstructure 145, the first semiconductor layer 120 may be exposed byetching a part of the second semiconductor layer 140 and the activelayer 130 of the light emitting structure 145 which corresponds to aregion where the first electrode 160 is to be arranged using apredetermined etching method, and the first electrode 160 may bearranged on the exposed region of the first semiconductor layer 120.

The first electrode 160 comes into ohmic-contact with the semiconductorlayer to facilitate supply of power to the light emitting structure 145.A metal and a light-transmitting conductive layer may be optionallyused. The first electrode 160 may include a conductive material. Forexample, the material includes at least one of nickel (Ni), platinum(Pt), ruthenium (Ru), iridium (Ir), rhodium (Rh), tantalum (Ta),molybdenum (Mo), titanium (Ti), silver (Ag), tungsten (W), copper (Cu),chromium (Cr), palladium (Pd), vanadium (V), cobalt (Co), niobium (Nb),zirconium (Zr), indium tin oxide (ITO), aluminum zinc oxide (AZO),indium zinc oxide (IZO), indium zinc tin oxide (IZTO), indium aluminumzinc oxide (IAZO), indium gallium zinc oxide (IGZO), indium gallium tinoxide (IGTO), antimony tin oxide (ATO), gallium zinc oxide (GZO), IrOx,RuOx, RuOx/ITO, Ni/IrOx/Au, and Ni/IrOx/Au/ITO, or an alloy thereof, butis not limited thereto.

The first electrode pad 162 may be formed on one side of the exposedpart of the first semiconductor layer 120. The position of the firstelectrode pad 162 is not limited and for example the first electrode pad162 may be adjacent to the edge of the second side S2 and the third sideS3.

In addition, the shape of the first electrode pad 162 is not limited andmay be selected from a variety of shapes including a circle, a rectangleand a semi-circle in view of convenience such as wire bonding.

In FIG. 2, the first electrode pad 162 has a ¼ circle shape, but is notlimited thereto.

In addition, the first electrode pad 162 may be provided with a roundregion adjacent to the edge between the second side S2 and the thirdside S3 to prevent breakage.

The first electrode arm 164 is connected to the first electrode pad 162and extends in a first direction (X).

In addition, the position of the first electrode arm 164 is not limitedand may be adjacent to the second side S2 of the light emittingstructure 145.

The second electrode 170 may be electrically connected to the secondsemiconductor layer 140. The second electrode 170 includes a secondelectrode pad 172 and a second electrode arm 174 arranged on the secondsemiconductor layer 140.

Here, the first electrode arm 164 and the second electrode arm 174 haveidentical lengths and one thereof may be greater, but is not limitedthereto.

In addition, a light-transmitting electrode layer 150 may be formed onthe second semiconductor layer 140. At this time, the second electrode170 may be arranged on the light-transmitting electrode layer 150.

The light-transmitting electrode layer 150 is formed through theentirety or on part of the outer side of the second semiconductor layer140 to prevent current crowding and discharge light emitted from theactive layer 130 to the outside.

That is, the light-transmitting electrode layer 150 for example containsat least one of ITO, IZO (In—ZnO), GZO (Ga—ZnO), AZO (Al—ZnO), AGZO(Al—Ga ZnO), IGZO (In—Ga ZnO), IrOx, RuOx, RuOx/ITO, Ni/IrOx/Au andNi/IrOx/Au/ITO, but is not limited thereto.

Here, a pattern (not shown) may be formed on the light-transmittingelectrode layer 150 and the pattern may be one of a dot pattern, aroughness pattern and a lattice pattern.

That is, the pattern can improve light extraction efficiency and preventa current crowding phenomenon.

In addition, a current blocking layer (not shown) may be arrangedbetween the light-transmitting electrode layer 150 and the secondelectrode 170, or between the light-transmitting electrode layer 150 andthe second semiconductor layer 140, or inside the light-transmittingelectrode layer 150, and the current blocking layer may at leastpartially overlap the second electrode 170.

The second electrode 170 supplies power to the light emitting structure145 and is made of the same material as the first electrode 160.

The second electrode pad 172 may be formed on the second semiconductorlayer 140 at the other side of the first electrode pad 162.

That is, the second electrode pad 172 may be formed adjacent to thefourth side S4 on the second semiconductor layer 140. In addition, theposition of the second electrode pad 172 is not limited and, forexample, the second electrode pad 172 may be arranged adjacent to theedge between the first side S1 and the fourth side S4 in view of currentdiffusion efficiency and luminous efficacy.

The shape of the second electrode pad 172 is not limited and may beselected from a variety of shapes including, but not being limited to, acircle, a rectangle and a semi-circle in view of convenient connectionto a power source by wire bonding.

The second electrode arm 174 is connected to the second electrode pad172 and extends in an opposite direction to the first direction (X).

With reference to FIG. 2, the second electrode arm 174 forms a step withthe second electrode pad 172, which is provided as one embodiment, butis not limited thereto.

In addition, the distance d1 from the first electrode arm 164 to thesecond electrode arm 174 in a second direction Y may be within a rangeof 25% to 75% of the width d of the second semiconductor layer 140 inthe second direction Y.

Here, the width d of the second semiconductor layer 140 means a distancebetween both sides in the second direction Y of the light emittingdevice of the second semiconductor layer 140, excluding the etchedregion of the second semiconductor layer 140.

The distance d1 between the first electrode arm 164 and the secondelectrode arm 174 is 25% to 75% of the width d of the secondsemiconductor layer 140 in the second direction Y to remove currentcrowding of the light emitting device.

And, the distance d2 between the first side of the second semiconductorlayer 140 and the second electrode arm 174 is 25% to 50% of the width orthe second semiconductor layer 140.

That is, the distance d1 between the first electrode arm 164 and thesecond electrode arm 174 and the between the first side of the secondsemiconductor layer 140 and the second electrode arm 174 causesimprovement in current diffusion efficiency of the light emitting deviceand a decrease in drive voltage, thus leading to improvement in currentdiffusion efficiency of the light emitting device, improvement ininternal quantum efficiency and an increase in light extractionefficiency.

Here, With reference to FIG. 3, the light emitting device 100 of Example2 exhibits a decrease of 0.08V in drive voltage (VF), as compared toComparative Example and a 3.16% increase in luminous efficacy, ascompared to Comparative Example. The 3% or more increase in luminousefficacy is a considerable increase which approaches theoretical limitsof luminous efficacy and in particular, 3% or more of an increase inluminous efficacy in small chips demonstrates applicability to smallchips.

In addition, comparing Example 1 and Example 2, and Comparative Example,the second electrode arm 174 readily diffuses current, luminous efficacyis improved and drive voltage is reduced, as it reaches the center ofthe second semiconductor current diffusion layer 140.

In addition, as drive voltage decreases, heat generation can be reducedduring use of the light emitting device 100.

The second electrode arm 174 may be formed in the center of the width ofthe second semiconductor layer 140 in the second direction Y.

That is, the second electrode arm 174 is arranged in the center of thewidth of the second semiconductor layer 140 in the second direction Y,and the light emitting device may extend in an opposite direction to thefirst direction X.

Accordingly, when the first electrode arm 164 is adjacent to the secondside S2, the distance d1 from the first electrode arm 164 to the secondelectrode arm 174 in the second direction Y is within a range of 25% to75% of the width Y of the width of the second semiconductor layer 140 inthe second direction Y.

In addition, the second electrode arm 174 may be connected to a lowerpart of the width d of the second electrode pad 172 in the seconddirection Y, but is not limited thereto.

In addition, the first electrode arm 164 and the second electrode arm174 may extend in the first direction X and in the opposite directionthereto.

In addition, the first electrode arm 164 and the second electrode arm174 may be arranged in parallel. When the first electrode arm 164 andthe second electrode arm 174 are parallel to each other in the firstdirection X, diffusion of current between the first electrode arm 164and the second electrode arm 174 is facilitated, drive voltage decreasesand luminous efficacy is improved.

FIG. 4 is a plan view illustrating a light emitting device in accordancewith another embodiment as broadly described herein.

The light emitting device 100 shown in FIG. 4 has the same configurationas the light emitting device 100 shown in FIG. 1. The light emittingdevice 100 shown in FIG. 4 has a configuration in which the top and thebottom thereof are reversed to those of the light emitting device 100shown in FIG. 1. At this time, the positions of the first to fourthsides (S1 to S4) and the positions of first and second electrodes 160and 170 are relative. That is, when the position of one is varied, theother may be relatively varied.

FIG. 5 is a plan view illustrating a light emitting device in accordancewith other embodiment as broadly described herein.

Referring to FIG. 5, the configuration of the light emitting device 200shown in FIG. 1 may differ from that of the light emitting device 100 inview of the position of the second electrode pad 272.

In addition, the light emitting device 200 of FIG. 5 includes the sameelements as the light emitting device 100 of FIG. 1 and a descriptionthereof is thus omitted.

The second electrode pad 272 may be formed in the center of the width ofthe second semiconductor layer 240 in the second direction Y. That is,when, like the second electrode arm 274, the second electrode pad 272 isformed in the center of the width of the second semiconductor layer 240in the second direction Y, light extraction efficiency of the lightemitting device can be further improved.

The position of the second electrode arm 274 connected to the secondelectrode pad 272 may be freely determined taking into consideration theluminous efficacy and current diffusion efficiency of the light emittingdevice.

The second electrode arm 274 may be connected to the top, center or thebottom of the width of the second electrode pad 272 in the seconddirection Y. That is, the second electrode arm 274 may be connected toany part of the width of the second electrode pad 272 in the seconddirection Y.

FIG. 6 is a perspective view of a light emitting device packageincluding the light emitting device in accordance embodiments as broadlydescribed herein.

FIG. 6 is a perspective view to see through one part of the lightemitting device package 300. Although the light emitting device package300 is a top view in this embodiment, the light emitting device package300 may be a side view and is not limited thereto.

Referring to FIG. 6, the light emitting device package 300 may include alight emitting device 310 and a body 320 in which the light emittingdevice 310 is arranged.

The body 320 may include a first barrier rib 322 arranged in a firstdirection (not shown) and a second barrier rib 324 arranged in a seconddirection (not shown) which crosses the first direction. The first andsecond barrier ribs 322 and 324 may be integrally formed and may beformed by an extrusion molding, etching or the like and is not limitedthereto.

That is, first and second barrier ribs 322 and 324 may be made of atleast one selected from resins such as polyphthalamide (PPA), silicon(Si), aluminum (Al), aluminum nitride (AlN), aluminum oxide (AlOx),photosensitive glass (PSG), polyamide 9T (PA9T), syndiotacticpolystyrene (SPS), a metal, sapphire (Al2O3), beryllium oxide (BeO),ceramic, and a printed circuit board (PCB).

The top shape of the first and second barrier ribs 322 and 324 may beselected from a variety of shapes including triangle, rectangle, polygonand circle depending on the application and designs of the lightemitting device 310, and is not limited thereto.

In addition, the first and second barrier ribs 322 and 324 form acavity(s) in which the light emitting device 310 is arranged. Thecross-section of cavity(s) may have a cup shape, recessed containershape or the like. The first and second barrier ribs 322 and 324constituting the cavity(s) may have an inclined face in a lowerdirection.

In addition, the plan surface of cavity(s) may be selected from avariety of shapes including triangle, rectangle, polygon and circle, butis not limited thereto.

First and second lead frames 313 and 314 may be arranged under the body320. The first lead frame 313 and the second lead frame 314 contain ametal such as titanium (Ti), copper (Cu), nickel (Ni), gold (Au),chromium (Cr), tantalum (Ta), platinum (Pt), tin (Sn), silver (Ag),phosphorus (P), aluminum (Al), indium (In), palladium (Pd), cobalt (Co),silicon (Si), germanium (Ge), hafnium (Hf), ruthenium (Ru), iron (Fe),and alloys thereof. In addition, the first and second lead frames 313and 314 may have a monolayer or multilayer structure, without beinglimited thereto.

The inner side of the first and second barrier ribs 322 and 324 may beinclined at a predetermined angle with respect to one of the first andsecond lead frames 313 and 314. The reflective angle of light emittedfrom the light emitting device 310 may be varied, depending on theinclination angle. Accordingly, the orientation angle of lightdischarged to the outside can be controlled. As the orientation angle oflight decreases, convergence of light emitted from the light emittingdevice 310 to the outside increases. On the other hand, as theorientation angle of light increases, convergence of light emitted fromthe light emitting device 310 to the outside decreases.

The inner side of the body 320 may have a plurality of inclinationangles and is not limited thereto.

The first and second lead frames 313 and 314 are electrically connectedto the light emitting device 310, are connected to positive (+) andnegative (−) electrodes of outer power sources (not shown),respectively, and supply power to the light emitting device 310.

In this embodiment, the light emitting device 310 is arranged on thefirst lead frame 313, the second lead frame 314 is spaced from the firstlead frame 313, and the light emitting device 310 is die-bonded to thefirst lead frame 313 and is wire-bonded to the second lead frame 314through a wire (not shown) to receive power from the first and secondlead frames 313 and 314.

Here, the light emitting device 310 may be bonded to the first leadframe 313 and the second lead frame 314, which have differentpolarities.

In addition, the light emitting device 310 is wire-bonded or die-bondedto the first and second lead frames 313 and 314, without being limitedin terms of connection formation method.

The light emitting device 310 is arranged in the first lead frame 313 inthis embodiment, but is not limited thereto.

In addition, the light emitting device 310 may be adhered to the firstlead frame 313 through an adhesive member (not shown).

Here, an insulating dam 316 may be formed between the first and secondlead frames 313 and 314 to prevent electric short between the first andsecond lead frames 313 and 314.

In this embodiment, the insulating dam 316 may have a semi-circular topand the shape thereof is not limited thereto.

The body 313 may be provided with a cathode mark 317. The cathode mark317 divides polarity of the light emitting device 310 (that is, polarityof the first and second lead frames 313 and 314), and may thus be usedto prevent confusion when first and second lead frames 313 and 314 areelectrically connected.

The light emitting device 310 may be a light emitting diode. The lightemitting diode may be a color light emitting diode to emit colored lightsuch as red, green, blue or white light, or an ultraviolet (UV) lightemitting diode to emit ultraviolet light, without being limited thereto.The light emitting device 310 mounted on the first lead frame 313 may bepresent in plural, at least one light emitting device 310 may be mountedon the first and second lead frames 313 and 314, and the number andposition of the light emitting device 310 are not limited.

Here, the light emitting device 310 may be one of light emitting devices100 and 200 shown in FIGS. 1, 4 and 5, but is not limited thereto.

The body 320 may include a resin material 318 filled in the cavity(s).That is, the resin material 318 may have a double-molded structure or atriple-molded structure and is not limited thereto.

In addition, the resin material 318 may be a film type and include atleast one of a phosphor and a light diffusion material.

In addition, the resin material 318 may include a light-transmittingmaterial which contains a phosphor and a light diffusion material, butis not limited thereto.

FIG. 7 is a perspective view of a backlight unit including a lightemitting device in accordance embodiments as broadly described herein,and FIG. 8 is a sectional view of the lighting device taken along theline A-A of the lighting device shown in FIG. 7.

Hereinafter, for better understanding, the lighting device 400 will bedescribed based on a longitudinal direction (Z), a horizontal direction(Y) vertical to the longitudinal direction (Z), and a height direction(X) vertical to the longitudinal direction (Z) and the horizontaldirection (Y).

That is, FIG. 8 is a sectional view of the lighting device 400 of FIG.7, taken along the cross-section of the longitudinal direction (Z) andheight direction (X) and seen from the horizontal direction (Y).

Referring to FIGS. 7 and 8, the lighting device 400 may include a body410, a cover 430 connected to the body 410 and an end cap 450 arrangedat both ends of the body 410.

A light emitting device module 440 is connected to the bottom of thebody 410 and the body 410 may be composed of a metal which exhibitssuperior conductivity and excellent heat release effects in order todischarge heat generated from light emitting device packages 444 to theoutside through the top of the body 410.

The light emitting device packages 444 exhibit improved bondingreliability and luminous efficacy and are advantageous in designing slimand small display devices due to roughness (not shown) provided in eachlead frame (not shown).

The light emitting device packages 444 are mounted in multiple colorsand multiple rows on the PCB 442 to form an array and may be spaced fromone another by a predetermined distance or by different distances, asnecessary, to control brightness. The PCB 442 may be a metal core PCB(MCPCB) or a PCB made of FR4.

The cover 430 may take the shape of a circle to surround the bottom ofthe body 410, without being limited thereto.

The cover 430 protects the light emitting device module 440 from foreignsubstances. In addition, the cover 430 prevents glare generated from thelight emitting device package 444 and includes diffusion particles touniformly discharge light to the outside. In addition, a prism patternor the like may be formed on at least one of the inner and outersurfaces of the cover 430. Alternatively, a phosphor may be applied toat least one of the inner and outer surfaces of the cover 430.

Meanwhile, the cover 430 should exhibit superior light transmittance, sothat it can discharge light generated from the light emitting devicepackage 444 through the cover 430 to the outside, and the cover 430should exhibit sufficient heat resistance so that it can endure heatemitted by the light emitting device package 444. Preferably, the cover430 is composed of a material including polyethylene terephthalate(PET), polycarbonate (PC), polymethyl methacrylate (PMMA) and the like.

The end cap 450 is arranged on both ends of the body 410 and may be usedto seal a power device (not shown). In addition, the end cap 450 isprovided with a power pin 452, allowing the lighting device 400 to beapplied to a conventional terminal from which fluorescent light has beenremoved, without using any additional device.

FIG. 9 is a perspective view of a liquid crystal display including alight emitting device in accordance with an embodiment as broadlydescribed herein.

FIG. 9 illustrates an edge-light type liquid crystal display device 500which includes a liquid crystal display panel 510 and a backlight unit570 to supply light to the liquid crystal display panel 510.

The liquid crystal display panel 510 displays an image using lightsupplied from the backlight unit 570. The liquid crystal display panel510 includes a color filter substrate 512 and a thin film transistorsubstrate 514 which face each other such that a liquid crystal isinterposed therebetween.

The color filter substrate 512 can realize color images to be displayedthrough the liquid crystal display panel 510.

The thin film transistor substrate 514 is electrically connected to aprinted circuit board 518 on which a plurality of circuit components ismounted through a driving film 517. The thin film transistor substrate514 responds to drive signals supplied from the printed circuit board518 and may apply drive voltage from the printed circuit board 518 toliquid crystals.

The thin film transistor substrate 514 includes a thin film transistorand a pixel electrode formed as a thin film on other substrates composedof a transparent material such as glass or plastic.

The backlight unit 570 includes a light emitting device module 520 toemit light, a light guide plate 530 to convert light emitted from thelight emitting device module 520 into surface light and supply the lightto the liquid crystal display panel 510, a plurality of films 550, 566and 564 to uniformize brightness of light from the light guide plate 530and improve vertical incidence, and a reflective sheet 540 to reflectlight emitted to the back of the light guide plate 530 to the lightguide plate 530.

The light emitting device module 520 includes a plurality of lightemitting device packages 524 and a PCB 522 on which the light emittingdevice packages 524 are mounted to form an array.

Meanwhile, the backlight unit 570 includes a diffusion film 566 todiffuse light incident from the light guide plate 530 toward the liquidcrystal display panel 510, a prism film 550 to concentrate the diffusedlight and thus improve vertical incidence and a protective film 564 toprotect the prism film 550.

FIG. 10 is a perspective view of a liquid crystal display including alight emitting device in accordance with another embodiment as broadlydescribed herein.

The contents illustrated and described in FIG. 9 are not mentioned indetail.

FIG. 10 illustrates a direct-type liquid crystal display device 600which includes a liquid crystal display panel 610 and a backlight unit670 to supply light to the liquid crystal display panel 610.

The liquid crystal display panel 610 has been described in FIG. 9 and adetailed explanation thereof is thus omitted.

The backlight unit 670 includes a plurality of light emitting devicemodules 623, a reflective sheet 624, a lower chassis 630 in which thelight emitting device modules 623 and the reflective sheet 624 areaccepted, and a diffusion plate 640 and a plurality of optical films 660arranged on the light emitting device modules 623.

Each light emitting device module 623 includes a plurality of lightemitting device packages and a PCB 621 on which the light emittingdevice packages 624 are mounted to form an array.

In particular, the light emitting device package 622 exhibits improvedbonding reliability and realizes slim and further reliable backlightunits 670 due to the roughness 170 formed in a region where the lightsource unit 130 and a wire 150 are wire-bonded to respective lead frames140 and 142.

The reflective sheet 624 reflects light generated by the light emittingdevice package 622 toward the liquid crystal display panel 610 toimprove luminous efficacy.

Meanwhile, light emitted from the light emitting device module 623 isincident on the diffusion plate 640 and an optical film 660 is arrangedon the diffusion plate 640. The optical film 660 includes a diffusionfilm 666, a prism film 650 and a protective film 664.

In the embodiments, the lighting device 400 and liquid crystal displays500 and 600 may be included in the lighting system and a lighting deviceincluding a light emitting device package may be included in thelighting system.

A light emitting device as embodied and broadly described herein mayallow which exhibits improved luminous efficacy, reduces drive voltage,and improves safety and reliability.

Any reference in this specification to “one embodiment,” “anembodiment,” “example embodiment,” etc., means that a particularfeature, structure, or characteristic described in connection with theembodiment is included in at least one embodiment of the invention. Theappearances of such phrases in various places in the specification arenot necessarily all referring to the same embodiment. Further, when aparticular feature, structure, or characteristic is described inconnection with any embodiment, it is submitted that it is within thepurview of one skilled in the art to effect such feature, structure, orcharacteristic in connection with other ones of the embodiments.

Although embodiments have been described with reference to a number ofillustrative embodiments thereof, it should be understood that numerousother modifications and embodiments can be devised by those skilled inthe art that will fall within the spirit and scope of the principles ofthis disclosure. More particularly, various variations and modificationsare possible in the component parts and/or arrangements of the subjectcombination arrangement within the scope of the disclosure, the drawingsand the appended claims. In addition to variations and modifications inthe component parts and/or arrangements, alternative uses will also beapparent to those skilled in the art.

1. A light emitting device, comprising: a light emitting structurearranged on the substrate, the light emitting structure including afirst semiconductor layer, a second semiconductor layer and an activelayer arranged between the first semiconductor layer and the secondsemiconductor layer; a first electrode electrically connected to thefirst semiconductor layer; and a second electrode electrically connectedto the second semiconductor layer, wherein the light emitting structurehas a top surface including a first side and a second side which faceeach other, and a third side and a fourth side which face each other,wherein the first electrode includes: a first electrode pad adjacent tothe edge of the second side and the third side in the exposed part ofthe first semiconductor layer; and a first electrode arm connected tothe first electrode pad, the first electrode arm extending in a firstdirection, the second electrode includes: a second electrode padadjacent to the fourth side on the second semiconductor layer; and asecond electrode arm connected to the first electrode pad, the firstelectrode arm extending in an opposite direction to the first direction,the distance from the first electrode arm to the second electrode arm inthe second direction is 25% to 75% of the width of the secondsemiconductor layer in the second direction.
 2. The light emittingdevice of claim 1, wherein the second electrode pad is formed adjacentto the edge between the first side and the fourth side.
 3. The lightemitting device of claim 1, wherein the second electrode pad is formedadjacent to the center of the width of the second semiconductor layer inthe second direction.
 4. The light emitting device of claim 1, whereinthe second electrode arm is formed in the center of the width of thesecond semiconductor layer in the second direction.
 5. The lightemitting device of claim 1, wherein the second electrode arm isconnected to an upper part of the width of the second electrode pad inthe second direction.
 6. The light emitting device of claim 1, whereinthe second electrode arm is connected to the center of the width of thesecond electrode pad in the second direction.
 7. The light emittingdevice of claim 1, wherein the second electrode arm is connected to alower part of the width of the second electrode pad in the seconddirection.
 8. The light emitting device of claim 1, wherein the firstelectrode arm and the second electrode arm are formed in parallel. 9.The light emitting device of claim 1, wherein at least one of the firstand second electrode pads has a circular shape or a shape having acurved part.
 10. The light emitting device of claim 1, wherein the firstand second electrode pads have different shapes.
 11. The light emittingdevice of claim 1, wherein the lengths of the first and second electrodearms are equivalent or one thereof is greater.
 12. The light emittingdevice of claim 1, further comprising: a light-transmitting electrodearranged between the second semiconductor layer and the secondelectrode, wherein the light-transmitting electrode layer has a pattern.13. The light emitting device of claim 12, wherein the pattern is one ofa dot pattern, a roughness pattern and a lattice pattern.
 14. The lightemitting device of claim 12, further comprising: a current blockinglayer arranged between the light-transmitting electrode layer and thesecond electrode, or between the light-transmitting electrode layer andthe second semiconductor layer, or inside the light-transmittingelectrode layer.
 15. The light emitting device of claim 14, wherein thecurrent blocking layer vertically partially overlaps the secondelectrode.
 16. The light emitting device of claim 1, wherein the firstelectrode is arranged in one part of the first semiconductor layerformed by mesa-etching the active layer and the second semiconductorlayer.
 17. A light emitting device comprising: a substrate; a lightemitting structure arranged on the substrate, the light emittingstructure including a first semiconductor layer, a second semiconductorlayer and an active layer arranged between the first semiconductor layerand the second semiconductor layer; a first electrode arranged on thefirst semiconductor layer, the first electrode including a firstelectrode pad and a first electrode arm extending from the firstelectrode pad in a first direction; and a second electrode arranged onthe second semiconductor layer, the second electrode including a secondelectrode pad and a second electrode arm extending parallel to the firstelectrode arm, wherein a first distance between the first electrode armand the second electrode arm is 25% to 75% of the width of the lightemitting structure, and a second distance between one side of the secondsemiconductor layer and the second electrode arm adjacent thereto is 25%to 50% of the width of the second semiconductor layer.
 18. A lightemitting device package comprising: a light emitting device including alight emitting diode; and a body including a first lead frame providedwith the light emitting device and a second lead frame spaced from thefirst lead frame, wherein the light emitting device comprises: asubstrate; a light emitting structure arranged on the substrate, thelight emitting structure including a first semiconductor layer, a secondsemiconductor layer and an active layer arranged between the firstsemiconductor layer and the second semiconductor layer; a firstelectrode arranged on the first semiconductor layer, the first electrodeincluding a first electrode pad electrically connected to the first leadframe and a first electrode arm extending from the first electrode padin a first direction; and a second electrode arranged on the secondsemiconductor layer, the second electrode including an second electrodepad electrically connected to the second lead frame and a secondelectrode arm extending parallel to the first electrode pad, wherein adistance between the first electrode arm and the second electrode arm is25% to 75% of the width of the light emitting structure.
 19. The lightemitting device package of claim 18, wherein a second distance betweenone side of the second semiconductor layer and the second electrode armadjacent thereto is 25% to 50% of the width of the second semiconductorlayer.
 20. The light emitting device package of claim 18, wherein thebody is provided with a cavity on the first and second lead frames, andincludes a resin material which fills the cavity and contains at leastone of a phosphor and a light diffusion material.